Windows Home Server was never a particularly popular product, but it did bring some interesting features to the table for the few who used it and became fans. One of these features was called Drive Extender. Its claim to fame was allowing users to pool their system's hard drives so they were seen by the operating system as one large hard drive. This obviated the need to keep track of free space across several disks, and it also allowed users to automatically mirror their data to multiple disks at once, keeping their files safe in the event of drive failure.

Microsoft killed Drive Extender not long before pulling the plug on the Windows Home Server entirely, but the intent behind it lives on in Windows 8's new Storage Spaces feature. "Storage Spaces is not intended to be a feature-by-feature replacement for that specialized solution," wrote Microsoft’s Rajeev Nagar in a blog post introducing the feature, "but it does deliver on many of its core requirements."

In essence, Storage Spaces takes most of Drive Extender’s underlying functionality and implements it in a way that is more technically sound. Early versions of Drive Extender sometimes corrupted data when copying files between drives and mangled file metadata, but the underlying filesystem improvements made to support Storage Spaces should make it much more robust, at least in theory.

Keeping your files safe

Storage Spaces allows you to take multiple disks of different sizes and interfaces—USB, SATA, SCSI, iSCSI, and SAS are among the supported interfaces—and group them together so the operating system sees them as one large disk. A group of physical disks is called a pool, and on top of that pool you can create one or more storage spaces. Each of these will show up to the operating system as a logical disk.

If all you want to do is combine two or more physical drives into one logical drive, you can do that by creating a "simple" storage space—however, if any one of your disks fails, you risk losing all of the data stored on that disk (and quite possibly data stored on the other disks as well). To prevent this, Storage Spaces offers several resiliency options to keep your files duplicated across all of the drives in the pool so disk failure won’t result in data loss. Allocating space to data duplication will reduce the amount of space available for data storage, but in almost all circumstances this is a sacrifice worth making.

There are three different data resiliency options available: two-way mirroring requires at least two physical disks, and will place a copy of each of your files on both drives; three-way mirroring requires at least five disks and will store a copy of each file on three of the five; and "parity" mode requires at least three disks and duplicates your data using less physical space on each disk, but has higher performance overhead—Microsoft recommends that it be used primarily for large files that are rarely changed.

All of these different resiliency types store data in 256MB "slabs" that are invisible to the user, with the goal of protecting data in case of disk failure. In a storage space with two-way mirroring enabled, a copy of every slab is kept on both disks so that if one goes down, no user data will be lost. The user should then be able to add new disks to the pool, at which point the rest of the disks in the pool will fill it up with the required slabs to restore data redundancy. Three-way mirroring gives you less usable space than two-way mirroring, but can tolerate the failure of up to two disks at once. Parity mirroring gives more usable space than either mirroring mode—a 20GB storage space configured with two-way mirroring will require about 40GB of physical disk space, but a 20GB parity storage space requires only about 30GB—but comes with the aforementioned performance hit.

In short, Storage Spaces offers the data protection provided by a RAID array without the rigid hardware requirements and planning required by RAID. Adding more space and swapping out bad disks can be done on-the-fly as needed, replicating the hassle-free storage experience espoused by home NAS providers like Drobo.

Thin Provisioning

Thin provisioning allows you to create logical drives that are totally independent of the underlying physical drives.

When you create a new storage space, you might notice you’re capable of setting a maximum size that greatly exceeds the amount of actual physical storage in your pool. You can even create multiple storage spaces per pool, each with different resiliency types and sizes. Microsoft calls this "thin provisioning."

Thin provisioning does have some uses for home users—if, for example, you’d like more frequently changed files to use two-way or three-way mirroring, but you’d like to store seldom-used files in Parity mode to save space—but it should prove especially useful for business users.

As an example: say you’ve got ten users and want to provide each of them with 100GB of space on your file server. You know that your users aren’t all going to use all of their space at the same time, so rather than having to purchase and setup 1TB of space all at once, Storage Spaces will allow you to create ten 100GB spaces on, say, a 500GB storage pool (or even less). Actual space on the physical disks will be allocated to your users as they actually use it, and if you get to the point where your 500GB storage pool is getting full, you can add more disks later on to expand the pool.

Thin provisioning will also allow you to expand the size of storage spaces as you go. Continuing our example from above, if you’ve got one power user who actually needs 200GB of space but most of your users are hardly using their allocated space at all, you can expand your power user’s storage space size without affecting your other users or needing to add more physical disks to your storage pool.

You will want to be careful about using too little physical space for too many storage spaces, though. When a storage space runs out of physical disk space, it will immediately unmount itself, causing any connections to the drive or file copy operations to be cut off. Files can still be accessed if the space is manually brought back online from within the Storage Spaces control panel, but you won't be able to copy anything else to it until you add more disk space to your storage pool.

Running out of physical disk space will unmount storage spaces until they're re-mounted manually or until more space is added.

92 Reader Comments

Aye the performance of parity storage spaces is pretty disappointing. I have a 3 x 2 TB parity setup using WD Green drives, and the write performance is only ~10-15 MB/s (after an initial burst like in the article).

Storage Spaces records information about pools and storage spaces on the physical disks that compose the storage pool. Therefore, your pool and storage spaces are preserved when you move an entire storage pool and its physical disks from one computer to another.

I can't stress enough how disappointing Storage Spaces is. This was *the* feature I really wanted Windows 8 to get right... and they failed. It was also the only reason I really wanted to upgrade my old boxes to Windows 8. I have dozens of old, albeit small, hard drives sitting in my basement that would seemingly work pretty well in a storage pool. However, after reading some early adopter testimonials, and this review, I don't think I ever want storage spaces touching any of my hard drives.

The fact that the system unmounts full drives without the ability to remount manually is beyond stupid. The lack of proper rebalancing is just laughable. Why not leave the feature out? It's clearly not ready. I thought MS learned their lesson with Longhorn/Vista.

It sounds great in principle. If Microsoft can get the caveats worked out, it might actually give me an incentive to assemble a Windows home server--something I'd never contemplated before, my environments being all Mac and Linux.

I don't understand the conclusion of the article.Storage Space is OBVIOUSLY not designed for enterprises. It offers a solution for home users, who can't afford a fancy menchy expensive RAID card to get things going. It's software RAID, so it's normal performance is slow. Like Home Server Drive Pool (or what ever it was called), it was duplicating files, like physically duplicating files on drives, when you made a RAID 1 setup out of it.

So I see it a great addition to Windows, and an excellent choice for someone who wants to setup a home server on a budget.

Why endure a whole new version of Windows to get drive pooling when third party solutions like Drive Bender exist now for Windows 7? When Microsoft dumped Drive Extender I gather it was envisioned to merely take its place for WHS, but means were found to "extend" the pooling to Windows 7 as well. And it's not the only product that rose to fill the need. I hope they next add "cloud pooling" to it, so I can aggregate and finally get some serious use from all the free cloud storage accounts I've amassed.

The testing done the article should probably have been done with normal internal drives rather than USB 3 drives for the simple point that it's possible that having 3x drives on the one USB controller slowed things down a bit.

I have set up a storage space on a HP Microserver running Windows Server 2012 and so far have been pretty happy with it, particularly compared to the Netgear ReadyNAS NVX I'm hoping to replace. The managability is great (Server 2012's interface for storage spaces is different from that of Windows 8), which is what I mainly wanted. VSS-backups, SMB3 access to my files, whilst having it all nicely protected. As someone else pointed out, if my Microserver dies I can just put my drives in USB caddies and plug them into another machine running Windows 8 or Server 2012 and I have my data. That was my worry with my ReadyNAS - if it died, I didn't have another ReadyNAS just sitting around ready to read the drives. (yes I have backups too, but belt & braces is nice)

Also, as far as I know, Storage Spaces doesn't support removable drives such as USB sticks, but it will support fixed drives such as USB external HDDs. That would explain why your USB sticks didn't work for you...

If Microsoft can sort out the rebalancing (maybe SP1?) then it's a very capable solution. I've made 4x 2TB Caviar Red drives in a storage space and have then carved out some virtual drives from that, most using striped parity (RAID 5) and a couple just striping the data (RAID 1). Because I can make many volumes and configure them how I want, I can say that I want 500GB (thinly provisioned) of space for documents, share that volume and then, at a volume level, turn on data deduplication (Server 2012 only).

When transferring data from the ReadyNAS I found that I didn't provision enough space in one of the volumes... No big deal - just right-click in server manager and extend the disk by a few hundred GB then extend the NTFS partition. Took maybe 15 seconds of clicking and there wasn't any downtime. I told Explorer to resume the copy and away it went.

Maybe Server 2012 does a better job in this department than Windows 8 client, but so far I'm pretty happy with the feature.

If Microsoft can sort out the rebalancing (maybe SP1?) then it's a very capable solution.

That would probably help the performance as well. My understanding is that WHS accepts all incoming data onto one drive (although which one drive it uses varies, after... SP2, I think), and then later rebalances that data out to the array. I'm guessing that doing so is what lets my WHS box accept data at 80-100MBps, since it's not doing the copying/parity calculation in real-time.

I don't understand the conclusion of the article.Storage Space is OBVIOUSLY not designed for enterprises. It offers a solution for home users, who can't afford a fancy menchy expensive RAID card to get things going. It's software RAID, so it's normal performance is slow. Like Home Server Drive Pool (or what ever it was called), it was duplicating files, like physically duplicating files on drives, when you made a RAID 1 setup out of it.

So I see it a great addition to Windows, and an excellent choice for someone who wants to setup a home server on a budget.

I don't understand your conclusion? Built in raid comes with the a vast majority of motherboards now, which means it is no more expensive than Storage Spaces. The only caveat is its not usually as user friendly to set up as storage spaces. Home users will not be buying $350+ raid cards with on board memory cache to begin with? I do applaud MS for offering someone without a raid option to do this but your argument is weak at best.

Having never been a home server user I've got no hands on experience, but the idea of it copying files around rather than doing things at the block level just seemed brittle and wrong to me (am I the only one?). What did it do with applications that held files open (eg many home accounting packages, things using MS Access DBs, etc) but made lots of changes to those files?

<speculation> I imagine that having 256MB chunks would allow a rebalancing algorithm to be included at a later date without too much effort. A one-off task, or a scheduled background maintenance operation, could do the balancing easily enough and do it all safely without ever having just a single copy of your bits. </speculation> The Server 2012 deduplication feature is implemented this way - it has a set of background tasks that run on a regular basis (admins who are very hands on can tweak these) and any changes it makes are always done with the ability to let the machine crash at any time and not lose data.

I don't understand the conclusion of the article.Storage Space is OBVIOUSLY not designed for enterprises. It offers a solution for home users, who can't afford a fancy menchy expensive RAID card to get things going. It's software RAID, so it's normal performance is slow. Like Home Server Drive Pool (or what ever it was called), it was duplicating files, like physically duplicating files on drives, when you made a RAID 1 setup out of it.

So I see it a great addition to Windows, and an excellent choice for someone who wants to setup a home server on a budget.

I don't understand your conclusion? Built in raid comes built in with the a vast majority of motherboards now, which means it is no more expensive than Storage Spaces. The only caveat is its not usually as user friendly to set up as storage spaces. Home users will not be buying $350+ raid cards with on board memory cache to begin with? I do applaud MS for offering someone without a raid option to do this but your argument is weak at best.

The built-in RAID on a lot of consumer motherboards relies on the software / driver to do a lot of the work. As you point out, real hardware RAID still costs a fair bit, particularly if RAM with battery backup, or SSD caching, is added. The main worry I still have with motherboard RAID is that it's not portable and, depending on the board, is kind of opaque, particularly when things go wrong.

Aside: The latest RunAsRadio podcast has Mark Minasi on talking about pros and cons of Storage Spaces

I take it the Storage Spaces functionality in MS Server 2012 Essentials is exactly the same? I could see a rebalancing feature showing up there first.

This is a step in the right direction, and it's good to know that if push comes to shove, I could recreate what I have in my WHS with good planning using Server 2012. But at the same time, I have no truly compelling reason to move off my functional WHS v1, since Server Essentials is expensive, and Win 8 doesn't have equivalent backup features.

(snip)Also, as far as I know, Storage Spaces doesn't support removable drives such as USB sticks, but it will support fixed drives such as USB external HDDs. That would explain why your USB sticks didn't work for you...(snip)

Was it because they were "removable" or because of the volume format? The flash drives like those that the author tried to use were almost certainly formatted as FAT32 volumes. I have 8GB and 16GB Sandisk Cruzer flash drives which I've reformatted as NTFS volumes to up the file size limitation (6 GB TrueCrypt volumes - yuk!). I wonder if that would work? I'm not finding anything about that in a quick Google search, but that might be worth a shot if someone really, really wants to use such drives. Personally, I wouldn't go there unless I was in a real pinch, or was pooling a very small amount of noncritical data for some reason.

(snip)Also, as far as I know, Storage Spaces doesn't support removable drives such as USB sticks, but it will support fixed drives such as USB external HDDs. That would explain why your USB sticks didn't work for you...(snip)

Was it because they were "removable" or because of the volume format? The flash drives like those that the author tried to use were almost certainly formatted as FAT32 volumes. I have 8GB and 16GB Sandisk Cruzer flash drives which I've reformatted as NTFS volumes to up the file size limitation (6 GB TrueCrypt volumes - yuk!). I wonder if that would work? I'm not finding anything about that in a quick Google search, but that might be worth a shot if someone really, really wants to use such drives. Personally, I wouldn't go there unless I was in a real pinch, or was pooling a very small amount of noncritical data for some reason.

Search for flipping removable bit on USB drives in your search engine of choice... It's a "property" of the USB drive - sticks tend to have it set on and USB HDDS have it off. Windows treats each type of drive differently. For example, you can't boot Windows off a USB stick normally (I bought a Lexar jump drive for our HP Microserver as I'd heard there's a bit flipping utility for the Lexar drives, but it's too old for the 64GB USB3 drive we bought)

Storage Spaces takes over the entire disk - it no longer has NTFS, FAT, etc on it per se. Windows actually gives it a GUID Partition Table rather than the old MBR based partition table (at least on my server it did) and makes it a dynamic disk rather than a basic disk. Odd but understandable - maybe MS is leveraging some of their old code with dynamic disks as this RAID 0/1/5 capability has been in Windows for several versions although it wasn't as flexible or easy to manage.

(snip)Also, as far as I know, Storage Spaces doesn't support removable drives such as USB sticks, but it will support fixed drives such as USB external HDDs. That would explain why your USB sticks didn't work for you...(snip)

Was it because they were "removable" or because of the volume format? The flash drives like those that the author tried to use were almost certainly formatted as FAT32 volumes. I have 8GB and 16GB Sandisk Cruzer flash drives which I've reformatted as NTFS volumes to up the file size limitation (6 GB TrueCrypt volumes - yuk!). I wonder if that would work? I'm not finding anything about that in a quick Google search, but that might be worth a shot if someone really, really wants to use such drives. Personally, I wouldn't go there unless I was in a real pinch, or was pooling a very small amount of noncritical data for some reason.

Search for flipping removable bit on USB drives in your search engine of choice... It's a "property" of the USB drive - sticks tend to have it set on and USB HDDS have it off. Windows treats each type of drive differently. For example, you can't boot Windows off a USB stick normally (I bought a Lexar jump drive for our HP Microserver as I'd heard there's a bit flipping utility for the Lexar drives, but it's too old for the 64GB USB3 drive we bought)

Storage Spaces takes over the entire disk - it no longer has NTFS, FAT, etc on it per se. Windows actually gives it a GUID Partition Table rather than the old MBR based partition table (at least on my server it did) and makes it a dynamic disk rather than a basic disk. Odd but understandable - maybe MS is leveraging some of their old code with dynamic disks as this RAID 0/1/5 capability has been in Windows for several versions although it wasn't as flexible or easy to manage.

I see. Good info, thanks. In other words, I was wrong: the volume format does not matter. The removable bit might, though. (I don't know why I seem to care - I don't have Windows 8. Just curious, I guess.)

I'm not sure I fully agree with your conclusions, Andrew. Yes, it's not a replacement for dedicated RAID hardware, but Storage Spaces is pretty flexible for home use, and it's "free". Performance is similar to other software-based RAID solutions, so (while disappointing) it's hard to ding Microsoft too much for that--you do get what you pay for. They appear to be using fairly good caching to smooth out typical random write scenarios though.

While there is room for improvement, I like the fact that you can mix USB 3.0 disks into a storage pool to create resilient volumes--something impossible to do via Windows' existing dynamic disks feature. You can also use "green" drives and other non-enterprise grade HDDs, which can cause problems for many hardware and software RAID solutions. And it's easy to expand (provided you follow Microsoft's instructions on the number of disks to add).

People fondly remember Drive Extender for having great flexibility for pooling disks. But DE offered no support for parity volumes of any kind.

I agree rebalancing would be a great addition to the feature (but in fairness, Windows did advise you to "add 3 disks" when your Parity volume became full). Perhaps they will add this in the future.

(snip)Also, as far as I know, Storage Spaces doesn't support removable drives such as USB sticks, but it will support fixed drives such as USB external HDDs. That would explain why your USB sticks didn't work for you...(snip)

Was it because they were "removable" or because of the volume format? The flash drives like those that the author tried to use were almost certainly formatted as FAT32 volumes. I have 8GB and 16GB Sandisk Cruzer flash drives which I've reformatted as NTFS volumes to up the file size limitation (6 GB TrueCrypt volumes - yuk!). I wonder if that would work? I'm not finding anything about that in a quick Google search, but that might be worth a shot if someone really, really wants to use such drives. Personally, I wouldn't go there unless I was in a real pinch, or was pooling a very small amount of noncritical data for some reason.

It's definitely not the format - they came as FAT32 I think, but when a drive is compatible with Storage Spaces it shows up regardless of format and is then re-formatted when it's added to the storage pool (I also reformatted as NTFS and blew all data away with Diskpart just to be sure).

What's peculiar is that I *could* make storage spaces with some USB drives back in the Consumer Preview phase, including SanDisk Cruzer drives - see the bottom of this page in the big Consumer Preview-era write-up I did while I was still at AnandTech: http://www.anandtech.com/show/5630/inde ... -preview/7

As I recall, even then I had some trouble getting the feature to work properly with flash drives - maybe MS chose to exclude some drives from being eligible rather than working to iron out the problems?

I've been testing Server 2012 Essentials for the last month and I've been toying with Storage Spaces as well. Our test system is running 5 disks, three of which are in a parity storage space (3 x Seagate 500GB 7200.11).

Locally, sequential reads from the space are in the realm of 150MB/s, while sequential writes are, as you noted, limited to 25MB/s after the initial burst. Not the best performance, but good for a collection of media files which won't need to be written to frequently. During writes, CPU usage is 20% (Phenom II X6 1055T @ 1.5 - 0.8GHz, which is as low as this chip will idle at stock.)

Our test system is also equipped with 16GB of memory, which Windows happily uses as a write cache when we're transferring files over the network to our test server. I've directly observed up to 13GB of data cached in memory as fast as the network interface will allow while the OS slowly writes the incoming data to the Storage Space at 25MB/s. From the client PC's perspective, the parity Storage Space's write speed is not a limiting factor until the OS runs out of available memory.

This would probably be a good solution for my HTPC/Media server for storing my 500+ DVD/B-Ray collection in .iso and .mp4 formats using parity mode. The files never change and I have the original DVD/B-Rays for backup in case of catastrophic loss. My motherboard only supports Raid 0 & 1 so no parity solution which is what I'm looking for.

I just replaced my home 2008 R2 server with a 5 x 1TB software RAID array with Server 2012 and a 3 x 3TB parity storage space and it's working as expected. Performance isn't an issue for me as this is primarily media storage. If anything, Storage Spaces is a little faster but it's also on a beefier machine. However, I fail to see much practical difference between the two other than (what I hope will be) the ease of growing an array under storage spaces which seems to be the sole killer feature. Using different size drives in either a parity or non-parity space is such a bad idea (inefficient and/or risky) that I don't fully understand why the option exists. (maybe something to temporarily take advantage of in a pinch)Also, from my point of view, StoragesSpaces obfuscates storage management somewhat. I found it tricky to setup. Straight up RAID is far more intuitive to me. Unless you can afford hardware RAID, the hardware and planning considerations are roughly the same, but maybe that's just me coming from a RAID perspective.

What are the options for migrating existing disks to a storage space configuration?

I have a typical SSD (boot/OS) + HDD (data/media) setup. I've purchased a second HDD of the same size that I'd like to use as a backup in a mirrored pool.

I was hoping to be able to setup a storage pool/space on the new drive, move my existing data into it and then format and redeploy the original drive as the mirror, but according to Microsoft's storage space FAQ, the resiliency type is immutable. So, if I started with "simple", I couldn't change to "mirrored" after the fact. Is it possible to start with mirrored and a single disk and add the second disk at a later time?

Unfortunately, I don't have enough spare disk lying around to completely free up the original drive for storage pool setup. Temporary cloud storage would likely be more trouble than it was worth, and I'm not really interested in buying and installing a 4th drive in this system.

Also, beyond the need to remain aware of where the file is actually stored, are there any major limitations or caveats to using hard-links to or from a virtual storage space volume? For applications like Steam that manage a huge amount of data, but don't have flexible tools for configuring where it's stored, the option of being able to move things and hard-link to them is important.

I was using Storage Spaces w/Parity on my Windows Server 2012 File Server (TechNet subscriber) and the performance was abysmal. What's more is that it took me days to figure out how to get it to actually build a storage pool. Only a few of my drives would appear as available to the pool. I could see and use them all from Applets, but I really had to dig in to it to find out why this was not working through the GUI.

It turns out that some drive controllers (RocketRAID 2314, for example) do not assign each individual disk a unique UniqueID - and the GUI will only show drives with a unique uniqueID. Same problem happened with on-board AMD RAID. I had to m,anually assign each drive (in the RAID BIOS) as a RAID Spare - unmarked drives shared the same UniqueID and thus the Storage Spaces GUI did not see them. Google Storage Spaces GUI and there is a detailed forum post on the MS Social site that goes into detail on this.

After using Storage Spaces for a month, I wiped the system and put everything back on the RAID card - performance was too abysmal.

Note: I built the Storage Spaces to test the feature and as a possible easy way to grow future storage over my RAID array (RocketRaid 2314 w/8x 1.5TB drives in 8-Bay CTI SATA enclosure).

This has come up elsewhere and it piqued my interest; what are the key differences between Storage Spaces in Win8 and LVM under Linux?

I only know SS from these articles, so this is somewhat incomplete.LVM does not have the equivalent of SS's 3-way copy (3 copies spread over 5 physical volumes)LVM does also have not a parity mode.

Parity can be obtained via the software RAID system, but it's a less flexible.Let's say you have 3 drives and you want a parity protected volume for some important stuff and a no protection volume for temporary files.With SS, you just add drives to the pool and then you can create, resize, delete, create again logical volumes, each with the desired resilience setting.

With software RAID, you need to plan ahead how much space you want with RAID5 and how much you want with RAID0.Then you create two partitions in each drive and then create two RAID volumes, one in RAID5 and another in RAID0. You can then use LVM to create logical volumes from those two RAID volumes.But what if you realize you gave too much space to RAID5 and too little to RAID0?It can be fixed but.. it's troublesome.

On the other hand, SS seems to only take entire drives to the pool. LVM (and RAID) can take partitions as well.

My need was fairly simple - give me more room on the drive that I store my games on. I had an extra disk I pulled from an external enclosure (the enclosure had failed, but the drive was good), so I made a pool out of the two disk and made a 2TB space. So now the space sits at 1.03TB of actual capacity and if I get close to that, I can just buy another 1TB drive and stick in my machine to make up for the needed space.

I wonder how many people actually HAVE 5 or more available drive connections without using an add-on controller card. That's even less likely if they're already trying to take advantage of multiple smaller drives.

Hmm.Does Windows 8 still support dynamic disks and mirroring (striping, parity, JBOD) like Windows 7 and the versions before?

I'm actually using mirroring via dynamic disks on my home file server because that way I'm not dependent on specific RAID controllers and neither on any driver support for specific ICHs or anything. Even stuffing the disks into USB enclosures and mounting them on a laptop does work.Performance for RAID 1 is great. Reading and writing large chunks gives me throughput very close to the raw speed of the slower of the two drives (the WD has slightly lower constant transfer rates). Iirc, the WD could do 115MB/s in benches tops and when copying from another, newer disk to the array I top out at about 110MB/s. CPU usage for this is some low single digit percentage with a C2Q.

Thinking about it, Storage spaces really seems to be a combination of the dynamic disks' JBOD feature with the others, like mirroring and parity. Dynamic disks can handle their features on a partition, or in MS speak "volume", level. Imagine two 1TB disks, each with a, say, 100GB volume and a 900GB volume. You could join the two small ones together to a 200GB entity, either as JBOD or RAID0 style, and have the 900GB chunks mirrored. You could also have a 1TB disk with an 80GB volume, add an old 80GB or more laptop drive and have it mirror that partition.I'm not sure if you could add mirroring to a partition spanning multiple drives under 7 or 2008R2. But if that would be possible, Storage spaces could just be a multitude of dynamic disk volumes under the hood, with 256MB each.

Another question, as this is badly done and can be a real world problem with Windows software RAID:What happens if you read from a mirrored storage space that rebuilds on a new disk?Is that usable, or does it sound like a toy machine gun with spinning disks?

The fact that the system unmounts full drives without the ability to remount manually is beyond stupid.

Possibly for security reasons? You do not want anyone remotely remount the drives when they were already unmounted for some reasons? Beside that, this idea was great from Microsoft but it seems it's 10 years too late from Microsoft for home users when internal hard drives nowadays are less than $200 for a 3 TB? How many 3TB do an average home user need? I take one for now.

Were you using virtual drives or physical drives? If you were using multiple virtual drives that would probably explain the performance hit when using Storage Spaces -- it's meant for physical drives, right?

One detail missing from this otherwise thorough review: When first setting up a Storage Space, do the drives added to the pool need to be completely empty?

I'm asking because I wonder about moving my home system from Windows 7 to Windows 8. I currently have my data on one 1TB drive, with a second 1TB drive used for a daily backup. (My OS is on a separate, small SSD.) How can I change my two data drives into a Storage Space?

If I'm right, and any new disk added to a Storage Space pool will be erased/reformatted/nuked, then will it be possible to transition from my current situation into a Storage Space situation without any pain?

What I took away from this article as negatives are slower write speeds than conventional methods, and you want to be adding more storage before you are getting too low with your existing storage.

I have a WHS v1 that I didn't migrate to the v2 because of lack of drive extender and the large amount of data I have (8TB of data redundant on 16TB across 8x2TB drives).

I already suffer from the slow write speeds with WHS v1, but it is a media server for me, so writes happen once per file, and then the rest is all reading, so that doesn't seem to bother me much, and I plan on migrating some of the 2TB drives out for 3+TB drives (which WHS v1 doesn't support).

So other than the painful, manual migration of my data, it sounds like storage spaces on server 2012 essentials may be the replacement for WHS that I was looking for.

The fact that the system unmounts full drives without the ability to remount manually is beyond stupid.

Possibly for security reasons? You do not want anyone remotely remount the drives when they were already unmounted for some reasons? Beside that, this idea was great from Microsoft but it seems it's 10 years too late from Microsoft for home users when internal hard drives nowadays are less than $200 for a 3 TB? How many 3TB do an average home user need? I take one for now.

BTRFS does this exact thing and people want ZFS to be able to do this. I don't see it being "too late".

The ability to have per volume redundancy without having to dedicate fixed portions of a drive to certain types while allowing re-balancing and keeping decent performance is the holy-grail of storage management.

MS didn't hit every check-box, but they got a few and this is only their first iteration.

" Microsoft for home users when internal hard drives nowadays are less than $200 for a 3 TB? How many 3TB do an average home user need? I take one for now."

Now add 3-way mirroring and quick rebuilds to that list. I would HATE to lose 3TB of data.